Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Stock-based compensation expense	$ 4.7	$ 3.7
Accrued liabilities	17.0	14.2
Deferred revenue	3.7	3.5
Net operating loss carryforwards - U.S.	0.2	1.9
Net operating loss carryforwards - Non-U.S.	2.4	3.1
Credits and incentive carryforwards	0.0	0.3
Deferred royalty revenue	0.3	0.2
Allowance for doubtful accounts	1.4	1.1
Deferred rent	7.4	6.2
Unrealized exchange losses, net	0.2	0.0
Other	0.6	0.3
Total deferred tax assets	37.9	34.5
Deferred tax liabilities:
Acquired intangible assets	(16.5)	(18.6)
Property, equipment and capitalized software	(26.7)	(24.6)
Unrealized exchange gains, net	0.0	(0.6)
Prepaid expenses	(7.1)	(3.9)
Investments in unconsolidated entities	(4.8)	(5.4)
Withholding tax - foreign dividends	(3.0)	(3.0)
Total deferred tax liabilities	58.1	56.1
Net deferred tax liability before valuation allowance	20.2	21.6
Valuation allowance	(2.0)	(2.0)
Total deferred tax liabilities	$ (22.2)	$ (23.6)